This invention relates to equipment for maintaining vehicular brake drums and is more particularly concerned with a gauge for measuring brake drum internal diameters.
In order to ensure proper performance of drumtype brake systems, brake drums which are out of round or which are of a diameter not within prescribed tolerances must be detected and either repaired or replaced. Such brake drum conditions are ordinarily detected by the use of a brake drum gauge, a class of device which is well known. Because brake drums are manufactured over a range of nominal diameters, it is usually desirable in practice that a brake drum gauge have the capability to measure drums of different sizes. Also, it is frequently desirable that a gauge of this type be applicable to brake drums in situ on the axle spindle of a vehicle or the mandrel of a repair shop turning lathe (used, for example, to recondition drums that are out of round) to avoid costly labor associated with removing and remounting the drums. Various gauges having one or both of the aforesaid characteristics have been proposed in the prior art. Generally, however, such devices have been beset with one or more of a number of problems such as high cost, complexity, difficulty in use, and excessive delicacy. Moreover, these devices have often required special micrometers, a factor which has contributed to the foregoing problems.